Quasi-one-dimensional uniform spin- 12 Heisenberg antiferromagnet KNaCuP2O7 probed by

Suman Guchhait

¹

,

Qing-Ping Ding

²

,

Madhusmita Sahoo

³

et al.

Abstract

We present the structural and magnetic properties of KNaCuP 2 O 7 investigated via x-ray diffraction, magnetization, specific heat, and 31 P and 23 Na NMR measurements and complementary electronic structure calculations. The temperature-dependent magnetic susceptibility and 31 P NMR shift could be modeled very well by the uniform spin-1 2 Heisenberg antiferromagnetic chain model with a nearest-neighbor interaction J/k B 58.7 K. The corresponding mapping using first-principles electronic structure calculations leads to J DFT /k B 59 K with negligibly small interchain couplings, further confirming that the system is indeed a one-dimensional uniform spin-1 2 Heisenberg antiferromagnet. The diverging trend of NMR spin-lattice relaxation rates ( 31 1/T 1 and 23 1/T 1 ) implies the onset of a magnetic long-range ordering at around T N 1 K. From the value of T N , the average interchain coupling is estimated to be J /k B 0.28 K. Moreover, the NMR spin-lattice relaxation rates show the dominant contributions from uniform (q = 0) and staggered (q = ±π/a) spin fluctuations in the high-and low-temperature regimes, respectively, mimicking one-dimensionality of the spin lattice. We have also demonstrated that 31 1/T 1 in high temperatures varies linearly with 1/ √ H , reflecting the effect of spin diffusion on the dynamic susceptibility. The temperature-dependent unit cell volume could be described well using the Debye approximation with a Debye temperature of D 294 K, consistent with the heat capacity data.

Spin dynamics of the one-dimensional double chain spin- 12 antiferromagnet KNaCuP2O7

“…spin oscillation signals, (ii) loss of initial asymmetry, and (iii) 1/3 recovery of the muon spin polarization. This observation is consistent with the previous NMR results, suggesting the long-range magnetic order around T N ∼ 1 K [30].…”

“…This analysis reveals that the muon relaxation rate is dominated by the q = 0 (q = π/a) term above T = 30 K (below T = 30 K). The essentially same trend is observed by μSR of DEOCC-TCNQF 4 [36] and 23 Na NMR of the studied compound [30]. Consistent with our μSR results, 23 Na 1/T 1 shows the switching of the dominant contribution from the high-T uniform to the low-T staggered excitations through T ≈ 20-30 K [30].…”

“…Optimized fittings of the χ tot (T ) data yield χ 0 = (1.40 ± 0.23) × 10 −5 emu/mol, C imp = 0.0017 ± 0.0005 emu mol −1 K, imp = −0.45 ± 0.03 K, the intrachain interaction J/k B ≈ 55 K, and the g factor of g ≈ 2.12. Overall, the extracted parameters are comparable to the reported values [30]. The impurity concentration is estimated to be 0.4%.…”

“…The interchain couplings J and J are much smaller than the intrachain interaction J due to the large interchain distance (5.676-5.772 Å). Recent 31 P and 23 Na nuclear magnetic resonance (NMR) and thermodynamic studies in conjunction with first-principles calculations show that KNaCuP 2 O 7 realizes a quasi-1D uniform S = 1 2 Heisenberg antiferromagnet with J/k B 58.7 K [30]. Magnetic long-range order was precluded down to 2 K, supporting the notion of weak, frustrated interchain couplings.…”

A Novel Mineral-like Copper Phosphate Chloride with a Disordered Guest Structure: Crystal Chemistry and Magnetic Properties

“…In the basal plane, the angle of Cu-O-Cu bond is equal to 107 o , which corresponds to an antiferromagnetic exchange interaction J between the nearest neighbor basal centers in accordance with the Goodenough-Kanamori-Anderson rules [28]. The magnetic exchange interaction between basal and apical ions passes through the intermediate PO 4 groups and is also usually antiferromagnetic J [29]. The fit of χ(T) curve in the model of S = 1/2 pentamers can be done based on the Hamiltonian with exchange interaction J between two spins expressed as Ĥ = −2JS 1 •S 2 [30].…”